Scala Reflection API

///////// Invocation of Scala collection object methods /////////

---
scala> import scala.reflect.runtime.universe._

scala> val mapClazz = scala.collection.immutable.Map.getClass
mapClazz: Class[_ <: scala.collection.immutable.Map.type] = class scala.collection.immutable.Map$

scala> val mirror = runtimeMirror(mapClazz.getClassLoader)
mirror: reflect.runtime.universe.Mirror = JavaMirror with ...

scala> val moduleSymbol = mirror.moduleSymbol(mapClazz)
moduleSymbol: reflect.runtime.universe.ModuleSymbol = object Map

scala> val instanceMirror = mirror.reflect(moduleSymbol)

scala> val toStringSymbol = moduleSymbol.typeSignature.member(TermName("toString"))
toStringSymbol: reflect.runtime.universe.Symbol = method toString

scala> instanceMirror.reflectMethod(toStringSymbol.asMethod)()    // OK
res9: Any = object Map

scala> val newBuilderSymbol = moduleSymbol.typeSignature.member(TermName("newBuilder"))
newBuilderSymbol: reflect.runtime.universe.Symbol = method newBuilder

scala> instanceMirror.reflectMethod(newBuilderSymbol.asMethod)()  // NG
scala.ScalaReflectionException: expected a member of <$anon: Symbols.this.ModuleSymbol with SynchronizedSymbols.this.SynchronizedTermSymbol>, you provided method scala.collection.generic.GenMapFactory.newBuilder
  at scala.reflect.runtime.JavaMirrors$JavaMirror.scala$reflect$runtime$JavaMirrors$JavaMirror$$abort(JavaMirrors.scala:115)
  at scala.reflect.runtime.JavaMirrors$JavaMirror.scala$reflect$runtime$JavaMirrors$JavaMirror$$ErrorNotMember(JavaMirrors.scala:121)
  at scala.reflect.runtime.JavaMirrors$JavaMirror$$anonfun$scala$reflect$runtime$JavaMirrors$JavaMirror$$checkMemberOf$1.apply(JavaMirrors.scala:214)
  at scala.reflect.runtime.JavaMirrors$JavaMirror.ensuringNotFree(JavaMirrors.scala:204)
  at scala.reflect.runtime.JavaMirrors$JavaMirror.scala$reflect$runtime$JavaMirrors$JavaMirror$$checkMemberOf(JavaMirrors.scala:213)
  at scala.reflect.runtime.JavaMirrors$JavaMirror$JavaInstanceMirror.reflectMethod(JavaMirrors.scala:247)
  at scala.reflect.runtime.JavaMirrors$JavaMirror$JavaInstanceMirror.reflectMethod(JavaMirrors.scala:233)



///////// Invocation of companion object methods /////////

---
scala> :paste
object TestObj {
  def method1(): String = "test"
  def method2[T](): T = null.asInstanceOf[T]
}

scala> import scala.reflect.runtime.universe._

scala> val mirror = runtimeMirror(this.getClass.getClassLoader)
mirror: reflect.runtime.universe.Mirror = JavaMirror with ...

scala> val instanceMirror = mirror.reflect(TestObj)
instanceMirror: reflect.runtime.universe.InstanceMirror = instance mirror for TestObj$@5afa3c9

scala> val toStringSymbol = typeOf[TestObj.type].member(TermName("toString"))
toStringSymbol: reflect.runtime.universe.Symbol = method toString

scala> instanceMirror.reflectMethod(toStringSymbol.asMethod)()  // OK
res6: Any = TestObj$@1f1c7bf6

scala> val test1Symbol = typeOf[TestObj.type].decl(TermName("method1"))
test1Symbol: reflect.runtime.universe.Symbol = method method1

scala> instanceMirror.reflectMethod(test1Symbol.asMethod)()     // OK
res2: Any = test

scala> val test2Symbol = typeOf[TestObj.type].decl(TermName("method2"))
test2Symbol: reflect.runtime.universe.Symbol = method method2

scala> instanceMirror.reflectMethod(test2Symbol.asMethod)()     // OK
res3: Any = null


---
scala> :paste
object TestObj {
  def method1(): String = "test"
  def method2[T](): T = null.asInstanceOf[T]
}

scala> import scala.reflect.runtime.universe._

scala> val clazz = TestObj.getClass
clazz: Class[_ <: TestObj.type] = class TestObj$

scala> val mirror = runtimeMirror(clazz.getClassLoader)
mirror: reflect.runtime.universe.Mirror = JavaMirror with ...

scala> val moduleSymbol = mirror.moduleSymbol(clazz)
moduleSymbol: reflect.runtime.universe.ModuleSymbol = object TestObj

scala> val instanceMirror = mirror.reflect(moduleSymbol)
instanceMirror: reflect.runtime.universe.InstanceMirror = instance mirror for object TestObj

scala> val toStringSymbol = moduleSymbol.typeSignature.member(TermName("toString"))
toStringSymbol: reflect.runtime.universe.Symbol = method toString

scala> instanceMirror.reflectMethod(toStringSymbol.asMethod)()
res6: Any = object TestObj

scala> val test1Symbol = moduleSymbol.typeSignature.decl(TermName("method1"))
test1Symbol: reflect.runtime.universe.Symbol = method method1

scala> instanceMirror.reflectMethod(test1Symbol.asMethod)()
scala.ScalaReflectionException: expected a member of <$anon: Symbols.this.ModuleSymbol with SynchronizedSymbols.this.SynchronizedTermSymbol>, you provided method TestObj.method1
  at scala.reflect.runtime.JavaMirrors$JavaMirror.scala$reflect$runtime$JavaMirrors$JavaMirror$$abort(JavaMirrors.scala:115)
  at scala.reflect.runtime.JavaMirrors$JavaMirror.scala$reflect$runtime$JavaMirrors$JavaMirror$$ErrorNotMember(JavaMirrors.scala:121)
  at scala.reflect.runtime.JavaMirrors$JavaMirror$$anonfun$scala$reflect$runtime$JavaMirrors$JavaMirror$$checkMemberOf$1.apply(JavaMirrors.scala:214)
  at scala.reflect.runtime.JavaMirrors$JavaMirror.ensuringNotFree(JavaMirrors.scala:204)
  at scala.reflect.runtime.JavaMirrors$JavaMirror.scala$reflect$runtime$JavaMirrors$JavaMirror$$checkMemberOf(JavaMirrors.scala:213)
  at scala.reflect.runtime.JavaMirrors$JavaMirror$JavaInstanceMirror.reflectMethod(JavaMirrors.scala:247)
  at scala.reflect.runtime.JavaMirrors$JavaMirror$JavaInstanceMirror.reflectMethod(JavaMirrors.scala:233)
  ... 33 elided

scala> val test2Symbol = moduleSymbol.typeSignature.decl(TermName("method2"))
test2Symbol: reflect.runtime.universe.Symbol = method method2

scala> instanceMirror.reflectMethod(test2Symbol.asMethod)()
scala.ScalaReflectionException: expected a member of <$anon: Symbols.this.ModuleSymbol with SynchronizedSymbols.this.SynchronizedTermSymbol>, you provided method TestObj.method2
  at scala.reflect.runtime.JavaMirrors$JavaMirror.scala$reflect$runtime$JavaMirrors$JavaMirror$$abort(JavaMirrors.scala:115)
  at scala.reflect.runtime.JavaMirrors$JavaMirror.scala$reflect$runtime$JavaMirrors$JavaMirror$$ErrorNotMember(JavaMirrors.scala:121)
  at scala.reflect.runtime.JavaMirrors$JavaMirror$$anonfun$scala$reflect$runtime$JavaMirrors$JavaMirror$$checkMemberOf$1.apply(JavaMirrors.scala:214)
  at scala.reflect.runtime.JavaMirrors$JavaMirror.ensuringNotFree(JavaMirrors.scala:204)
  at scala.reflect.runtime.JavaMirrors$JavaMirror.scala$reflect$runtime$JavaMirrors$JavaMirror$$checkMemberOf(JavaMirrors.scala:213)
  at scala.reflect.runtime.JavaMirrors$JavaMirror$JavaInstanceMirror.reflectMethod(JavaMirrors.scala:247)
  at scala.reflect.runtime.JavaMirrors$JavaMirror$JavaInstanceMirror.reflectMethod(JavaMirrors.scala:233)
  ... 33 elided